cleaned up usage of AST_BlockStatement

The following nodes were instances of AST_BlockStatement: AST_Scope,
AST_SwitchBlock, AST_SwitchBranch.  Also, AST_Try, AST_Catch, AST_Finally
were having a body instanceof AST_BlockStatement.

Overloading the meaning of AST_BlockStatement this way turned out to be a
mess; we now have an AST_Block class that is the base class for things
having a block of statements (might or might not be bracketed).  The
`this.body` of AST_Scope, AST_Try, AST_Catch, AST_Finally is now an array of
statements (as they inherit from AST_Block).

Avoiding calling superclass's _walk function in walkers (turns out we walked
a node multiple times).

1 files changed, 8 insertions, 6 deletions

diff --git a/lib/output.js b/lib/output.js
index e5c1c26b..5df1c2c4 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -467,12 +467,14 @@ function OutputStream(options) {
         self.body.print(output);
         output.semicolon();
     });
-    DEFPRINT(AST_BlockStatement, function(self, output){
-        var body = self.body;
+    function print_bracketed(body, output) {
         if (body.length > 0) output.with_block(function(){
             display_body(body, false, output);
         });
         else output.print("{}");
+    };
+    DEFPRINT(AST_BlockStatement, function(self, output){
+        print_bracketed(self.body, output);
     });
     DEFPRINT(AST_EmptyStatement, function(self, output){
         output.semicolon();
@@ -563,7 +565,7 @@ function OutputStream(options) {
             });
         });
         output.space();
-        self.body.print(output);
+        print_bracketed(self.body, output);
     });
     DEFPRINT(AST_Lambda, function(self, output){
         self._do_print(output);
@@ -701,7 +703,7 @@ function OutputStream(options) {
     DEFPRINT(AST_Try, function(self, output){
         output.print("try");
         output.space();
-        self.btry.print(output);
+        print_bracketed(self.body, output);
         if (self.bcatch) {
             output.space();
             self.bcatch.print(output);
@@ -718,12 +720,12 @@ function OutputStream(options) {
             self.argname.print(output);
         });
         output.space();
-        self.body.print(output);
+        print_bracketed(self.body, output);
     });
     DEFPRINT(AST_Finally, function(self, output){
         output.print("finally");
         output.space();
-        self.body.print(output);
+        print_bracketed(self.body, output);
     });
 
     /* -----[ var/const ]----- */